I'm upgrading my toolbox and am ready to buy a longer tele. I've been giving a lot of consideration to the 400 F/5.6 prime and the 100-400 zoom. I used a zoom a little last year doing some racing shots at Lime Rock, and liked what I got from it, but after reading a lot of reviews on both lenses, I have yet to make a choice.
My concerns with the reviews: Prime- Pro; super sharp IQ. Con; Lack of IS
Zoom- Pro; wider range of focal length, has IS. Con; IQ not quite as sharp as prime, dust getting inside the lens.

I guess my biggest concerns weighing in favor of the prime is the IQ, and the revies I've read of the dust getting in the zoom lens. Just how much IQ difference can really be expected (or seen) between the two? Is there really that much of a problem with the sealing on the lens that it sucks in the dust? If you have one (or both) of these lenses, what are your experiences?

Lens to be used on 7D mainly (5DII some possibility too) for wildlife and some auto-racing.
Thanks,
Tim

The dust problem is way over blown. If you stand in a dusty room and deliberately pump the zoom back and forth as fast as you can then sure, you can get some dust in there. For most people, under normal use, dust is never an issue.

Many zoom lenses pump air in and out even when you twist them rather than being a pump action. Go look at at 16-35L, 24-105L or any of them that have a moving rear (or even front) element.

I have the 400 5.6 / 7D combo and it's been great for BIF, etc.
I also recently borrowed the 100-400 and got some very sharp images (tripod mounted).

My decision was based on weight/size (400 wins), price and reach. What I noticed is that I am when shooting wildlife, I almost always want maximum reach; that cinched it for me. Why have a 100-400 if I'm always going for the long end? Instead I got the 400 and I'm happy with it. My next step down in reach is the 70-200 f4is if I am needing a wider view.

I've had the 100-400 for about 6 years. I use it mostly in Florida, birding, so maybe not the dustiest environment. Never an issue with dust however, and the weight and versatility of the zoom have been real pluses for me. I have done some macro-like shots, some portraits with it.
I have had the chance to try the 400.

In general I think the supposed improvement in IQ from a prime vs a zoom is sometimes overblown. At least that's been my experience using two primes and three zooms. And I'd be willing to bet that if you hand-hold much of the time the difference between IS and non-IS is going to be more important more often in terms of IQ than prime vs zoom, assuming both are top-notch lenses as the two you're considering are.

Obviously that's a generalization, it could be that when comparing two specific lenses the prime might be noticeably better than the zoom. It just hasn't been with the primes and zooms I own.

I owned both lenses and eventually settled on the 100-400mm becuase it is so versatile and, at least to my eyes, delivered pictures as good as the 400mm which I ended up selling.

I have used the 100-400mm to shoot BIF, take pics from the kayak and during all my son's outdoor sporting events. Having the ability to zoom and properly frame your subject is really beyond value. Unless you are always going to need 400mm, then you should serious consider the 100-400mm. Despite the fact that I had the 400mm and 500mm, it really has become my goto lens.

I've had my 100-400 for 7 years and have used it in a wide variety of environments without dust issues. I find the IS invaluable and its IQ is quite good throughout its range. My base three lens travel kit consists of 24-105, 100L, and 100-400 so I use it for everything above 100. I can't compare to the 400 prime but I have the 70-200 f4 IS and don't choose between them based IQ.

I keep my 100-400mm on my camera at least a good 90% of the time - never noticed any dust. I love that lens, and IS sure seems to come in handy for me on those cold winter day early morning hikes... but I do almost always find myself shooting at or near 400mm, so I too contemplate going prime every now and then.

Another vote for the 100-400L. The prime has zero versatility. Dust has been a non issue for me in the 100-400. Mine is at least three years old and well traveled. Zero dust. IQ between the zoom and prime is negligible.
Decide if you need/want the flexibility of the zoom or will you ALWAYS be at 400mm. That is the best way to choose between two great options.

M Vers wrote:
I've had my 100-400 for years and have yet to run into any dust issues. Unless you're shooting at a dusty race track/rodeo or in a windy desert environment frequently I wouldn't worry at all.

In terms of IQ, I guarantee no one would be able to tell them apart in a blind test. AF, however, is a different story; The prime is better in this area.

Basically, it comes down to AF speed vs versatility.

I believe this to be true. I have had my 100-400 for only a year and have had it on my 7D often and have yet to have to manually clean the sensor of any dust and also see no dust within the lens. IQ is very good. If AF speed of the 400 F/5.6 prime is similar to that of the 70-200 mk II then AF is certainly not as fast but still very good. My guess is that IS is probably 2-3 stops but technique is very important on long tele's. Below is full shot and 100% crop @400mm F/5.6. 50 LR sharpening applied to both.

I agree that AF on the 100-400L isn't as fast as the 70-200/2.8L II, which I also have, especially in low light. It seems to lock focus very nicely with my 1D-series bodies, but not quite so well in low light with my 5D (centre point AF in all cases).

That's my post with a series of images I shot with the 100-400, and the race cars were at Lime Rock.

My vote is for the 100-400. I love mine. Part of the reason is the versatility, but also because I think 400mm is probably too long 90% of the time at Lime Rock. I shoot there regularly, and I don't even bring the 100-400 anymore. I use a 70-200 for just about everything on the track. Galleries are here:http://msalvetti.smugmug.com/Auto-Racing

(Edit: I just noticed you live in DE, so maybe just happened to be at Lime Rock and it's not your regular track. Still, I use my 100-400 for baseball, soccer, air shows, nature, and even dragonflies and butterflies. It's a great, versatile lens. If I ever buy a 400 prime, I'd still keep the 100-400.)

Tim, dust is not generally an issue with the 100-400 zoom. I have rented one in the past but chose to buy a 400 5.6. It is an amazing lens for it's size and will deliver supurb images with enough light. I recently used a 400 5.6 from the stands at an NFL game and was amazed at the IQ of the images. I do not think I would have been admitted with the zoom due to it's much larger size. I shoot a lot of wildlife and if 400 mm will get the job accomplished it is my go to lens because of the smaller size. The 400 prime has fast AF and IS is a hinderance with shutter speeds above 1/500th of a second. On the other hand the 100-400 has the ability to be an all round lens taking the place of a 70-200 and a long prime.

I use my 100-400 for HS football and soccer. I have not had any issues with dust or focus speed in these applications using a 1D3. As others have said, it's a very versatile lens. I have no experience with the prime so I cannot offer a comparison.

I guess my biggest concerns weighing in favor of the prime is the IQ, and the revies I've read of the dust getting in the zoom lens. Just how much IQ difference can really be expected (or seen) between the two? Is there really that much of a problem with the sealing on the lens that it sucks in the dust? If you have one (or both) of these lenses, what are your experiences?

Lens to be used on 7D mainly (5DII some possibility too) for wildlife and some auto-racing.
Thanks,
Tim...Show more →

I would suggest the 100-400 for everything except fast moving wildlife (birds mainly). The IQ is nearly identical between the two. Dust is not a problem. For auto racing and airshows the 100-400 is about as good as it gets in that focal length. Wide open the 400 5.6 is going to be a bit better in focus accuracy, but the 100-400 can be stopped down slightlly to help mask any focus errors that might occur. When panning for auto racing using smaller apertures is good anyhow.